docs: def inertia_tensor(self):
          """
          The inertia tensor of the source for the rotation around its
          center of mass.
          """
  
          mu = self.moments_central
          a = mu[0, 2]
          b = -mu[1, 1]
          c = mu[2, 0]
          return np.array([[a, b], [b, c]]) * u.pix**2